Mobility is important. Wireless-communication infrastructures have enabled the dawn of all sorts of devices that no longer require hardwired connections when sending and receiving data. Such devices, and many others, require electronic power to function; in many cases, this power comes from a rechargeable battery. In a way, the rechargeable battery limits the mobility of these devices because it must be plugged in to charge. As a result of the need to recharge, the mobility of these devices is compromised for extended durations (e.g., when the device is plugged into an electrical outlet). Recently, wireless charging has emerged as an option for powering and recharging various devices. With wireless charging, the devices are less reliant on wired connections and the presence of traditional outlets. One method for wireless power transmission includes generating an oscillating magnetic field by using an A/C signal to drive a solenoid or source coil. A charging device uses the changing magnetic flux to generate a current in a coil of its own. It is advantageous if both the source of the oscillating magnetic field and a coil circuit in the device to be charged are resonant at the same frequency. This allows for improved power transfer when compared to non-resonance-matched setups.
Furthermore, it is desirable that the source coil is driven at a high power level because this enables a greater effective charging range. However, the magnetic field acts more akin to a transmission line and less like a power store. When transmitted power is not used, the system loses this energy in the form of heat. If the source coil is driven and little of the energy carried by the oscillating magnetic field is absorbed by charging devices, it is analogous to running a current through a copper wire without a sufficient load being connected. The system will run hot and there will be a risk of overheating the circuitry that drives the coil. One known approach is to decrease the amount of power used to drive the source coil. This improves efficiency and prevents overheating, but reduces the effective charging range. Accordingly, for this reason and others, there is a need for methods and systems for an improved magnetic resonant power supply.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.